An electrooptical precision distance and angle measuring arrangement is known from the corporate paper "Hewlett-Packard Journal", No. 3, Apr. 1983. In this arrangement, the distance information is obtained via the Doppler effect. A laser is provided which supplies two optical beams having different frequencies and different polarizations. The superposed beams reach a first optical receiver as well as a beam splitter which deflects one of the two beams and transmits the other beam. The beam deflected by the beam splitter impinges on two deflecting mirrors and returns to the beam splitter. This beam traverses a predetermined optical path. The beam transmitted by the beam splitter having the other frequency likewise impinges on two deflecting mirrors and is returned to that particular location in the beam splitter at which the deflected returned beam impinges. The return beams are superposed in the beam splitter and are incident upon a second optical receiver.
The two deflecting mirrors in the beam path of the beam transmitted by the beam splitter are movably mounted. With a movement, the optical distance traversed by the transmitted beam is increased or decreased. The movement leads to an increase or reduction of the frequency of the reflected beam (Doppler effect).
The first optical receiver supplies an output signal having a frequency proportional to the frequency difference of the two beams generated by the laser. The second optical receiver supplies an output signal having a frequency proportional to the frequency difference of the two beams generated by the laser and is reduced or increased by the Doppler frequency. The two output signals are applied to a frequency counter which determines the difference of the two signals with the result being the Doppler frequency which is a measure of the velocity of the moving deflecting mirrors. The traversed path or angle is determined from the velocity.